1. Field of the Invention
The present invention relates to a damper device, especially to a damper device located in a place where an inputted force for rotary motion or linear motion is transmitted to a passive member, and an image forming apparatus such as a copier or a printer.
2. Description of Related Art
Generally, in an electrophotographic image forming apparatus, a rotary drive for an image forming process requires highly-accurate transmission of a rotative force. However, a rotary drive system includes factors of load fluctuations in a rotating direction or vibrations (speed fluctuations) in the rotating direction, such as a motor and engagements between gears, which inhibits an improvement in accuracy of the transmission of the rotative force. Meanwhile, simplification of the system for transmitting a rotative force has been demanded so as to reduce the cost, and for realizing this, vibrations (speed fluctuations) that occur upstream from the drive system need to be effectively blocked by a simple means so as not to be transmitted to downstream.
Japanese Patent Laid-Open Publication No. H7-210032 describes a drive system for rotating a photoreceptor drum. In the drive system, a side surface member with an elastically deformable inner peripheral part is attached to the end surface of the photoreceptor drum, and an engaging hole is made in the inner peripheral part to be engaged with an engaging pin of a driving gear. By the drive of the driving gear, the side surface member is elastically deformed. Then, by a reaction force of the deformation, the photoreceptor drum is rotated.
Japanese Patent Laid-Open Publication No. H10-268602 describes a drive system including a rotor, a drive source for driving the rotor, a first elastic member that transmits a rotative force from the drive source to the rotor and that determines the natural frequency of the drive system made up of the rotor and the drive source through its elastic deformation behavior, and a second elastic member that acts on the elastic behavior of the first elastic member so as to increase the damping characteristics.
Japanese Patent Laid-Open Publication No. 2002-174932 describes a drive system including a brushless motor that generates motive power, a photoreceptor drum that is driven to rotate by the motive power of the brushless motor, a gear train that transmits the motive power of the blushless motor to the photoreceptor drum through a plurality of gears, a rubber vibration isolator that is located between the gears so as to prevent transmission of vibrations to the photoreceptor drum, and a photoreceptor gear that is provided in the photoreceptor drum and connected to the gear.
The measures to isolate vibrations described in Japanese Patent Laid-Open Publication Nos. H7-210032, H10-268602 and 2002-174932 are not necessarily preferable in terms of simplification of the structure as well as effects, and a more effective measure to isolate vibrations has been desired.